1. Field of the Invention
The present invention relates to an optical interconnect.
2. Discussion of the Background
In portable devices such as a cell phone, data transmission is often carried out among multiple printed wiring boards (PWBs) each having a different function. For example, image data or the like are transmitted from a main printed wiring board to a printed wiring board which is arranged for image display.
In U.S. Pat. No. 7,130,511, a flexible signal cable is described for optically transmitting data between printed wiring boards. The flexible signal cable described in U.S. Pat. No. 7,130,511 is formed with a flexible wiring board, a light-emitting element and a light-receiving element electrically connected to the flexible wiring board, and an optical waveguide formed on the flexible wiring board to optically connect the light-emitting element and light-receiving element.
The flexible signal cable described in U.S. Pat. No. 7,130,511 is structured as an optical interconnect by connecting both ends to their respective printed wiring boards. In an optical interconnect using a flexible signal cable, data to be transmitted from a printed wiring board on the data-transmitter side are transmitted to a light-emitting element as an electrical signal. The light-emitting element converts the electrical signal to an optical signal. The optical signal converted by the light-emitting element is transmitted from the light-emitting element to a light-receiving element, passing through an optical waveguide formed on the flexible signal cable. The light-receiving element receives the optical signal transmitted to the light-receiving element and converts the optical signal to an electrical signal. Then, the electrical signal converted by the light-receiving element is transmitted to a printed wiring board on the data-receiver side.
As so described, in an optical interconnect using a flexible signal cable, data are transmitted as optical signals between two printed wiring boards through a light-emitting element, an optical waveguide and a light-receiving element.
FIG. 1 is a cross-sectional view schematically showing an example of a conventional optical interconnect in which printed wiring boards for data transmission face each other. As optical interconnect 110 in FIG. 1 shows, even if printed wiring board (111a) and printed wiring board (111b) face each other, data are transmitted as an optical signal through light-emitting element (112a), optical waveguide 115 and light-receiving element (112b). The arrow with a broken line in FIG. 1 schematically shows the direction in which the optical signal is transmitted. The optical signal passes through the optical waveguide.
When printed wiring board (111a) and printed wiring board (111b) face each other, flexible wiring board 113 always stays in a bent condition. Thus, optical waveguide 115 formed on flexible wiring board 113 is required to be flexible so that it curves, and does not bend, when it is folded. In addition, optical waveguide 115 is required to have features such as lowered optical signal loss even when it is curved. As a result, there is a concern that the material and the method for manufacturing an optical waveguide of an optical interconnect are limited.
The contents of U.S. Pat. No. 7,130,511 are incorporated herein by reference in their entirety in this application.